The present invention is directed to a control knob assembly for a cooking appliance and particularly to a control knob assembly for a gas cooking appliance including a pop-out control knob located in a knob housing within the control panel of the cooking appliance, for providing a flush-appearing control panel surface when the cooking appliance is not in use, and for providing a two-step actuation control of the cooking appliance when it is desired to energize the cooking appliance.
A safety requirement of the American Gas Association is that, in order to open a gas valve in a cooking appliance, a two step operation must be used. Typically, such an operation includes a first step of depressing or pushing a knob, and a second step of turning a knob to select a desired setting. Existing gas valves or power switches designed for use in cooking appliances are designed to accommodate the required two-step operation, typically by incorporating a spring-loaded actuator shaft which must be axially displaced to release a catch before being rotated to select a desired setting.
U.S. Pat. No. 3,100,404, Boeddeker et al., discloses a retractable knob for use with a rotatable power switch in a cooking appliance. A spring clip captures a shaft end when the control knob is depressed, thereby positively latching the knob in the retracted position. To release the control knob, a release member comprising an annular member moves along the shaft to release the clip. The control knob is urged forwardly by a spring, and moves to an extended position where it may be grasped by the user. A disadvantage to the disclosed knob is that operation of the knob in a two-step operation is not enabled. A further disadvantage to the disclosed knob is that the mechanism for operating the control switch remains engaged when the control knob is depressed to retract the knob, potentially permitting inadvertent actuation of the power switch.
U.S. Pat. No. 3,269,211, McGarry et al., discloses a retractable control knob for use with a rotatable power switch in a cooking appliance. A spring is captured by a catch element when the control knob is depressed, thereby retaining the knob in a recessed position. When it is desired to release the control knob, the handle is depressed inwardly, thereby releasing the spring, and accordingly the control knob, which is spring-loaded to automatically extend to a usable position. A disadvantage to the disclosed knob is that operation of the knob in a two-step operation is not enabled. A further disadvantage to the disclosed knob is that the mechanism for operating the control switch remains engaged when the control knob is depressed to retract the knob, potentially permitting inadvertent actuation of the power switch.
U.S. Pat. No. 4,300,525, Delgado et al., discloses a non-retractable two-step knob assembly for a gas cooking appliance. A cam portion on the control knob shank displaces a spring-loaded member when the knob is rotated to an "off" position, which member then returns to an extended position after the raised cam portion passes by, thereby preventing one-step rotation of the knob assembly once the knob assembly is placed in the "off" position. The valve may be opened by pushing the knob assembly inwardly, which compresses a spring contained within the knob assembly. The cam moves forwardly to clear the spring-loaded member, thereby permitting the knob assembly to be rotated to an "on" position. While the described arrangement permits two-step operation, a retractable control knob for a cooking appliance is not provided.
The present invention overcomes the disadvantages of the previous control knobs for cooking appliances by providing a retractable two-step knob assembly for a cooking appliance. More particularly, the present invention includes a knob assembly which both provides a means for sequentially depressing a valve or switch shaft, then rotating the shaft.
An advantage of the present invention is the capability of providing two-step operation of a valve or switch, while permitting retraction of the knob to provide additional safety and a flush control panel surface appearance. A further advantage of the present invention is to provide a control knob assembly which may be retracted only when the control or switch is in an "off" position. Yet another advantage of the present invention is the ability to provide a retractable two-step switch, which is prevented from inadvertent movement to an "on" position when the control knob is in the retracted position.
Yet another advantage of the present invention is the ability to provide a retractable, two-step switch which requires a minimum number of components, for reduced cost, improved ease of manufacture, and increased reliability. A further advantage of the present invention is improved tactile response and feedback to the user.